Cadmium, a component of cigarette smoke, is a human carcinogen. Acute exposure to cadmium causes p53 dependent apoptosis. However at lower concentrations, cells have an ability to survive and resist apoptosis by up-regulating metal chelating, antioxidant proteins such as metallothionein. This adaptive phenomenon could result in the propagation of DNA damaged cells that eventually may lead to tumorigenesis. The long-range goal of the project is to study how chronic adaptive response to heavy metal exposure causes cancer. The objective of the proposal is to examine the role of c-maf, a basic leucine-zipper motif which binds to consensus DNA, in regulating metallothionein gene expression. The hypothesis is that c-maf negatively regulates metallothionein promoter. However, in cadmium adapted cells, c-maf-mediated repression on metallothionein is abolished and correlates with inhibition of apoptosis. The rationale is that this proposal may identify c-maf as the upstream factor that regulates heavy metal adaptation. The approach will be to demonstrate the functional role of c-maf on metallothionein gene expression by transient expression assays. The aims of the proposal are (1) to examine the expression of c-maf and metallothionein in normal, immortalized and cancer oral epithelial cells in the presence or absence of cadmium adaptation and (2) to study the function of c-maf in metallothionein transcriptional activity. We expect to demonstrate that c-maf directly binds to the MARE-TRE or MTLF/ARE sequences and inhibit metallothionein promoter in normal and non-adapted cells. In immortalized and cancer cells, as well as in cadmium adapted cells, we expect that the c-maf repression on metallothionein is abolished and is correlated with the inhibition of apoptosis. The data obtained will be significant, since the study may suggest a role of c-mar in differentially regulating metallothionein and p53 genes, which are implicated in apoptotic pathway. Also, these studies will provide further mechanistic information about the regulation of metallothionein and cadmium adaptation.